1. Field of the Invention
The present invention pertains to tools for handling elements to be installed in or removed from pressurized vessels. Specifically, it pertains to a tool for installing or removing coupons, anodes and like elements in a pressurized vessel, pipeline or the like.
2. Brief Description of the Prior Art
Frequently it is desirable to insert into a pipeline, or other pressurized vessel, a coupon from which can be measured the rate of corrosion due to the fluids being transported through the pipeline or vessel. It may also be desirable to insert an anode into the pipeline or vessel for retarding corrosion of the vessel material. In addition, other elements such as temperature probes, transducers, etc. are from time to time inserted into such pressurized environments. If the pipeline or other vessel is empty, installation of such coupons, anodes, probes, etc. is a relatively easy task. However, if the pipeline or other vessel is in operation, the pressure therein increases the difficulty and hazard of such a task.
Since it is expensive to arrest the flow in and evacuate fluids from an operating pipeline or vessel, it is desirable that methods and apparatus be provided which will allow installation or removal of elements from the pipeline or vessel while it continues to operate. Accordingly, various extractor tools have been developed in recent years to accomplish such a task. One such tool is shown in U.S. Pat. No. 2,770,532. With this extractor tool, the element is inserted or removed by a rack and pinion arrangement. The tool is designed to be left in place at all times and to retrieve the coupon, anode or other elements, it is necessary to rotate a disc on which the housing is disposed. The length of such a tool is unduly long. Furthermore, if a number of elements are required, the cost of supplying a tool for each element may become prohibitive.
In U.S. Pat. No. 2,870,629, an extractor tool is disclosed which is designed for removal and use at a number of locations. This is made possible through the use of a check valve arrangement. Reciprocation of the mechanism for inserting or removing the coupon is accomplished by applying pressure to a piston like carrier. The operation of such a tool requires a source of fluid pressure and the design is relatively expensive to manufacture and maintain.
Another pressure-operated extractor tool is shown in U.S. Pat. No. 3,031,742. This tool is actuated by pressure directly from the pipeline or vessel in which the element is installed. Thus, it is not necessary to have an independent source of pressure. This tool is also relatively complex to manufacture and maintain. Furthermore, to engage a coupon or other element with a receiving fitting in the vessel or to remove one therefrom, it is necessary to rotate the entire tool.
Very recently, another extractor tool has been developed by Brown Oil Tools, Inc., which is removable and manually operable, eliminating some of the disadvantages of prior extractor tools. Such a tool is equipped with two mechanisms, one for providing a relatively large amount of reciprocal movement for inserting and removing the coupon or other element and the second for providing rotational movement of the coupon or other element upon engagement with a fitting by which said element is held in the pipeline or vessel. The first mechanism involves a rack and pinion having a crank, rotation of which causes the rack to move in and out for installing and removing the element. When the element is extended into the pipeline or vessel by a sufficient amount, the second mechanism, a worm and worm wheel arrangement, is engaged and operated. Rotation of the worm which engages a worm wheel attached to the element holder causes the holder to rotate for threadedly engaging a fitting to hold the element in place.
While the aforementioned tool is better in some respects to the prior art, it has certain inherent problems. At least two of these problems are due to the rack and pinion mechanism. Such a mechanism causes the tool to be unduly long. This is particularly a problem when the coupon or other element to be installed is to be installed in a fitting beneath a pipeline, requiring extensive soil removal, or where there are limited clearances between the pipeline and adjacent equipment. Another problem is the danger when pressure in the tool is not equalized with the pipeline upon removal of the element. In such a case, pipeline pressure may cause the rack to be quickly forced to an extended position, rapidly rotating the crank with potential danger to the operator and damage to the tool. Another disadavantage is the fact that the crank for operation of the reciprocating mechanism and wheel for operation of the rotating mechanism may be separated by several feet in large models, requiring two operators.
The fact that extractor tools for handling coupons, anodes, and the like during installation in and removal from pressurized pipeline or vessels continues to be developed, is an indication of a need for better tools. While prior art tools have evolved for the better, they still have characteristics which are not totally acceptable.